Mantis embodies the principles of a hunter, Black Widow-style, but in ass-whoppingly gargantuan form. She is a single and multitarget DPS burst hero, with additional scout, harrassment and stealth capabilities. She has splendid movement and one mobility ability, two different stealth effects, a high damage AoE, and also throws in self-healing (though not quite at Aphid's level), a little stun/crowd control through equipment, and very high armor piercing into the mix. And she is, being a legendary hero, obscenely powerful. But really not overbearingly so. Forget yourself for a few seconds, and a group of the weakest enemies can bring her down, much like any other hero in the game. However, because of her particular focus and sustainability, she can make a mockery of some otherwise particularly hard missions, in some particular contexts. But it does not seem to me that these qualities are anything that would unbalance gameplay in PvP.